First CCS program and having troubles working with registers

[Guest]

Sorry, but this is my first time using this compiler and I am trying to convert a program from a different compiler and lots of things are different. Primarily, I am having trouble working with the PIC registers. I don't see anyplace where they are assigned names so I don't know how to convert all the instructions that directly modify hardware registers.

For example, I have the following code for setting up the USART:

txsta = 0b00100100;
rcsta = 0b10000000;

And setting some options:

option_reg.NOT_RBPU = 0; // PortB pullups activated
option_reg.INTEDG = 1; // interrupt on rising edge

And waiting for a character from the USART:

while (pir1.RCIF == 0) ;
char c = rcreg;

And testing for receive errors:

if(rcsta.OERR == 1){
rcsta.CREN = 0;
rcsta.CREN = 1;
return OVERFLOW;
}
if(rcsta.FERR == 1){
return FRAMINGERR;
}

How do I do all these things with CCS? Thanks!

[PCM programmer]

All of this is done at a higher level with CCS functions.

[Guest]

Thanks. It is a bit disconcerting not having direct control over the bits in the registers. I had looked briefly at #use rs232 but didn't see the bits I needed to set and also thought that there would be no way would the compiler designers would use RS232 to mean UART. I mean really, they are NOT the same thing. I do not have any RS232 hardware attached to my PIC, for example.

But that aside, looking at #use rs232, it is hard at first glance to see which settings correspond to the equivalent bits of txsta and rxsta.

I guess you just never have to set transmit enable or receive enable because the getc and putc routines do it for you, is that it?

To specify that the UART is running asynchronously, do you just NOT set SYNC_SLAVE or SYNC_MASTER?

Is just not necessary to do anything other than set the baud rate high enoug to cause the BRGH bit to be set?

Finally, how do you enable continuous receive? The manual mentions that SYNC_MATER_CONT makes the RS232 line a synchronous master mode in continuous receive mode, implying that there is a separate way to enable continuous receive.

What would be great is some examples of using the UART with varying configurations. Or even a discussion of the topic in the manual, explaining what happens to the registers when you make certain choices in the #use RS232 directive.

I miss having control of the registers even if it does save me a byte or two, if that even really is the case.

Anyway, thanks for the help!

[PCM programmer]

Here's how to see what the compiler is doing:

If you're using MPLAB, go to the Project Menu, then to Build Options,
and on the Compiler tab, set the List file format to Symbolic.

Also, edit the .H file for your PIC and comment out the #nolist line
near the top.

Then make a test program, compile it, and look at the .LST file.
You can see the values that the compiler puts into the SFR registers.

[Ttelmah]

In a sense, this is the key point about using a compiler, rather than assembler. With CCS, if (for instance), you change from using a PIC 16 chip, to a PIC 18, provided you have used their functions, the compiler does the work 'for you'.
You can directly access registers, using the #byte, and #bit functions, _but_ you really should try to think 'high level', and _not_ use these, unless you really have to.

Best Wishes

[RLScott]

[treitmey]

And to access the registers use #bit or #byte to overlay a variable on the register.

below show in hex for a 18F4525

[Guest]

Good information, everybody! Thanks.